provided code

src/tests/lib.pm

@@ -0,0 +1,19 @@
+use strict;
+use warnings;
+
+use tests::random;
+
+sub shuffle {
+    my ($in, $cnt, $sz) = @_;
+    $cnt * $sz == length $in or die;
+    my (@a) = 0...$cnt - 1;
+    for my $i (0...$cnt - 1) {
+	my ($j) = $i + random_ulong () % ($cnt - $i);
+	@a[$i, $j] = @a[$j, $i];
+    }
+    my ($out) = "";
+    $out .= substr ($in, $_ * $sz, $sz) foreach @a;
+    return $out;
+}
+
+1;